Process for adsorbing pentavalent vanadium values from strongly acid leach liquors



No Drawing. Application August 9, 1955 Serial No. 527,402

' 4Claims. 01.23-19 This invention relates to an improved process of adsorbing vanadium compounds from acid leach liquors on anion exchange resins.

Vanadium compounds have been obtained from their ores by leaching with such acids assulfuric acidto produce a strongly acid leach liquor. This has been particularly the case with ores which contain both vanadium and uranium as the acidleaching is one of the best methods of extracting uranium values from ores. Inthe case of uranium-vanadium ores, it is customaryto treat the acid liquor to adsorb uranium leaving asubstantially uranium barren leach liquor containing part -or all vof the vanadium. Similarly acid leaching of vanadium ores that do not have any recoverable uranium content produce the same type of acid leach liquor. Attempts have.

been made inthe past to adsorb vanadium in the penta valent form -by anion exchange resins particularly strong base anion exchange resins. These-attempts, however,

:failed in practical operationand have been abandoned;

The difiiculty encounteredwhichrendered the procedure impractical on a large scale lies in the fact that when acid leach liquors containing vanadium in fair concentration, the order of 2.5-5 g./l,, it was necessary to use a somewhat elevated temperature in order to obtain practical outputs. Whenever the higher temperature was used with anion exchange resins conventionally arranged in a series'of columns, the column encountering the fresh liquor with the highest vanadium concentration soon plugged up with a precipitated polyvanadate, which is referred to in the art as red cakeJ For simplicity, this shorter designation will be used inthe remainder of this specification. A plugged resin bed'became useless because the red cake cannot be economically and rapidly removed.- As a result the adsorption of vanadium on hanion exchange resin arranged in beds was formerly economically impractical.

In the past adsorption on ion exchangeresins from acidic ore pulp andacid leach liquor, the so-called resinin-pulp process, has achieved considerable commercial success in the recovery of uranium. Theproblem of red cake precipitation would be expected to be even more serious in a resin-in-pulp process because the precipitate would be-lost with the pulp, whereas in a resinbed process, at least it is available in concentrated space 'even though its recovery is atthe present time prohibitively costly. I v

The present invention depends on a surprising discovery. When a resin-in-pulp process is used with pulp containing an"-acid leach liquor and a concentration of vanadium which resulted in reclcake precipitate in a resin bed atv practical operating temperatures, no precipitation occurs. In other words,;itis possible to adsorb vanadium by anionexchange resin in a pulp containing'vanadium United States Paten ice Patented May V17, 1950 from red cake precipitation and the process proceeds smoothlyand easily. -It is another advantage of the presentinvention that any of the standard operating techniques used in resin-in-pulp processes may be employed here. No new techniques need be learned. Thus, for example, a series of cells may be used with submerged vertical screens with resin beads having a rapid flow of liquid over the screen at a flat angle which are described and-claimed in the copending application of David Kaufman and George W.'Lower, Ser. No. 441,356, filed July 6, 1954 now Patent No. 2,808,928. Apparently the improved results which are obtained with the present invention depend on the use of relatively large resin particles which can beretained on a screen of mesh and which can be distributed uniformly throughout -thevolume of the material from which vanadium is adsorbed because if a typical cell suitable for resin-in-pulp operations is used, for example a cell of the type described in the aforementioned application, the same satisfactory results are obtained if the resin beads are contacted with clear leach liquor which has been separated (from the pulp by conventional means. In other words, the present invention'depends for its effectiveness on-the contact of relatively] large resin particles with a fairly large volume of the liquor or pulp 'containingthe vanadium with suitable agitation and having suflicient time to permit satisfactory adsorption at the; elevated temperature which permits satisfactory outputs. In neither case is there any noticeable precipitation of red cake.

When the resin-in-pulp process is used, which normally means a series of cells or a series of adsorption stages,

it is ordinarily desirable to carryout the whole adsorption cycle from pulp because for mechanicalreasons if the equipment is used that would handleresin in pulp,- there is no point in wasting money in eifecting a liquidsolid separation for most of the cycles. It is, of course,

- possible to proceed in this manner because the red cake precipitation is encountered only when the vanadium concentration is fairly-high. In the case of operations with leach liquor, it is onlyne cessary that the adsorption onto the relatively large resin beads be effected for one or more stages until the vanadium contenthas been brought down below the level at which red cake precipitation becomes a problem in column work. Thereafter, the

7 partially exhausted leach liquor, may be adsorbed in columns if this is desired. Preferably, however, even in the case of operation with leach h'quor the whole adsorption cycle is efiected with, relatively large resin particles such "as beads.

' It is an advantage of -the present invention that the conditions other than the contacting of the vanadium bearing material with the resinare'not changed. As has been pointed out above, the temperature range for maxi-v mum adsorption remains the same and the same pH considerations apply, that is to say the pH must be prevented fro'rnris'ingtoo high, i.e. as high as 2. Otherwise a precipitation of insoluble vanadium compounds "will take place. Thelower limit of pH is approximately 1.3, as below this pH there is a tendency to transform the vanadium compounds at least partially into products containing vanadium as the cations. which are not adsorbable;

It should be noted that the pH range given above which is not different from that required in columnoperation is mentioned at'room temperature. sorbing system at the higher temperature the customary thermal effects willbe noted, which means that when in the leach liquor .at the same concentration which gives trouble in columns and at the same'temperature, 50 -7 0 C., which permits rapid adsorption.

By means of the present invention it is possible to ob tain good vanadium adsorptionswithout significant losses measured in the hot pulp, the pH would be slightly higher.

Throughout the specificationwhen pH is referred to, it is the pH measured at room temperature. K The invention will be -described ingre'atet"detail"incofijunction with the followingspecific examples.

In'the actualadn Example I A series of 14 cells provided with vertical screens and with means for directing a rapid substantially vertical flow of liquid and air bubbles over the screen were set up. These cells are of the type described in the abovereferred to application of Kaufman and Lower. Each cellv contained mesh strong base anion resin of the quaternary ammonium polystyrene-divinyl benzene type described in U.S. Patent No. 2,591,573, and sold by Rohm and Haas under the designation XE-123, the volume of resin being about one fifth of that of the cell. A sulfuric acid leach liquor of pH 1.5 was used. The operation was continuous, running six cells in series for adsorption, six for elution and two in standby condition. Whenthe first cell of the adsorption cycle has reached maximum loading, it is cut out, a fresh cell cut in at the end andthe feed transferred to the second cell. This continues until the resin in six cells is fully loaded with vanadium when a conventional elution cycle is started. This elution cycle is conventional, using sulfurous acid and as the invention is not concerned with this elution cycle, it will not be described in greater detail. The concentration of the leachv liquor used varied slightly from cycle to cycle as this was obtained from a practical ore. The following table shows the metallurgical results of 13 cycles together with their average.

.The above 13 cycles were carried out under conditions which assured that all of the vanadium in the leach liquor was in the pentavalent form. This was effected by adding sufficient sodium chlorate to prevent the formation of any reduced vanadium compounds. The residence in each cell of the string of six was 60 minutes, and cell temperature was maintained at 55 C.

Example II The procedure of Example 1 was repeated with a somewhathigher grade leach liquor. A very high loading of 140 grams of V20 per liter of wet settled resin Wm ob- 4 Example 111 The procedure of Examples 1 and 2 was repeated with an ore pulp in contact with the acid liquor. The percentage of solids was 9% and sands larger than the openings in the screens were removed by classification. A loading of 82 grams V 0 per liter of Wet settled resin was obtained. The results are shown in the following table.

Vanadium Content of Pulp Solids Cycle No. EfeegL/l Balrrgnli RPercent ecovery g a 5 g 2 5 Head, Tails,

Per- Percent cent V305 V205 Average 2. 20 0. 31 85. 9 0. 51 0. 52

I claim:

1. A process for adsorbing pentavalent vanadium values from a strongly acid leach liquor bearing said values and having a concentration of the vanadium values sufficiently high so that when contacted with fixed anion exchange resin beds at 50-70 C. precipitation of insoluble polyvanadates takes place, which comprises contacting with agitation anion exchange resin particles which are retained on a 20 mesh screen with said leach liquor at temperatures of 50-70" C-., and continuing the adsorption on the resin particles until the concentration of vanadium values in the leach liquor drops below that at which insoluble polyvanadates precipitate in a quiescent fixed resin bed at 5070 C.

2. A process according to claim 1 in which the leach liquor after adsorption of the vanadium values by the resin particles is separated therefrom and is then contacted with fixed quiescent anion exchange resin beds to adsorb the remaining vanadium values thereof.

3. A process according to claim 1 in which the adsorption of the vanadium values from the leach liquor is effected in a plurality of contacts with successive portions of the anion exchange resin particles with agitation until the leach liquor is substantially exhausted of vanadium values.

4. A process according to claim 3 in which'the leach liquor also contains finely ground, leached ore particles suspended therein and the said leached ore particles are separated by screening from each portion of the resin particles.

References Cited in the file of this patent UNITED STATES PATENTS 2,648,601 Byler et a1 Aug. 11, 1953 2,671,035 Bergman Mar. 2, 1954 2,756,122 McLean July 24, 1956 OTHER REFERENCES V McLean et al. in US. 'Atomic Energy Commission,

publication ACCO-63, July 30, 1954 (note especially pp. 47 and 48). V

Abrams et al. in US. Atomic Energy Commission, publication ACCO-53, July 10, 1954 (especially page6).

Salmon et al.: Journal of the Chemical Society (1952), pp. 2324-2326.

Sussman et al.: Industrial and Engineering Chemistry, vol. 37, No. 7, pp. 618 -624. 

1. A PROCESS FOR ADSORBING PENTAVALENT VANADIUM VALUES FROM A STRONGLY ACID LEACH LIQUOR BEARING SAID VALUES AND HAVING A CONCENTRATION OF THE VANADIUM VALUES SUFFICIENTLY HIGH SO THAT WHEN CONTACTED WITH FIXED ANION EXCHANGE RESIN BEDS AT 50-70*C. PRECIPITATION OF INSOLUBLE POLYVANADATES TAKES PLACE, WHICH COMPRISES CONTACTING WITH AGITATION ANION EXCHANGE RESIN PARTICLES WHICH ARE RETAINED ON A 20 MESH SCREEN WITH SAID LEACH LIQUOR AT TEMPERATURES OF 50-70*C., AND CONTINUING THE ADSORPTION ON THE RESIN PARTICLES UNTIL THE CONCENTRATION OF VANADIUM VALVES IN THE LEACH LIQUOR DROPS BELOW THAT AT WHICH INSOLUBLE POLYVANADATES PRECIPITATE IN A QUIESCENT FIXED RESIN BED AT 50-70*C. 